Thermostatic device



Dec. 21,1937. 5 P. VAU HN 2,102,656

THERMOSTATIC DEVICE Filed Feb. 8, 1936 INVENTOR SIDNEY P. VAUGHN Ma, M

ATTORNEY Patented Dec. 21, 1937 UNITED STATES THERMO STATIC DEVICE Sidney P. Vaughn, United States Navy, flickerman, Miss.

(Granted-under the act or March 3, 1883, as amended April so, 1928; are 0. e. 757) The invention described herein may be manumodifications thereof as will be apparent to those iactured and used by or for the Government of skilled in the art to which the invention apperthe United States of America for governmental tains. purposes without the payment of any royalties Reference should be had to the accompanying thereon or therefor. drawing forming a part of this specification, in 5 This application covers the subject matter of which abandoned application Serial No. 646,122, filed Fig. 1 is a longitudinal sectional view of the December '7, 1932, on a Thermostat and improvesnap acting thermostatic element embodying my ments thereon. invention.

The invention relates to a thermostat and more Fig. 2 is a longitudinal sectional view of a 10 particularly to a thermostat having a, snap acmodified form of Fig. 1. tion. Fig. 3 is a plan view of the snap disc and The principal object of this invention is to holder. provide a flexible metallic thermostatic element Fig. 4 is a, longitudinal sectional view of the m which will expand and contract with a snap snap disc and holder. movement in response to temperature and pres- Like figures refer to like parts throughout the sure changes, to be used in the operation of several views. valves, electric switches, etc., where a snap move- Referring to the drawing, Fig. 1 illustrates ment is desired. one form of the snap acting thermostatic ele- In my construction I employ a flexible metallic ment embodying my invention, in which numeral 20 bellows or diaphragm, closed at both ends, and I designates a flexible metallic bellows, formed formed with a number of annular folds or conwith a number of annular folds or corrugations,

volutions, which expands and'contracts in length containing a thermo-sensitive fluid which causes in response directly to changes in internal presthe bellows to expand and contract in response to sure, which, in the case of temperature contemperature or pressure changes. The lower end trols, is. created by the employment within the of the bellows is closed by a disc head 2, and the bellows of a thermo-sensitive fluid. This type upper end of the bellows is closed by a disc head i of bellows -is used in many types of temperature it having a threaded tubular boss t extending upandpressurecontrols. Heretofore the expansion wardly and provided for assembling the element and contraction has been gradual in response to in the casing in which it is to be used. Extend-' temperature or pressure changes, making it ing from the tubular boss is a tubular member 5 necessary to employ various kinds of snap action which connects the bellows with a bulb 6 which devices between the bellows and the valve or also contains some of the thermo-sensitive fluid. switch in order to produce a snap' movement in A dished plate holder i, flanged upwardly at In this invention I provide within the bellows is clamped between the edge of the upper disc an overcenter spring or snap disc' so arranged head 3 and an annular internal shoulder formed as to cause the bellows to expand and contract in the upper end of the bellows. Theflanging with a snap movement instead of expanding and of the plate holder 1 forms an annua ehourcontracting with a gradual movement, thus simder 8 between the plate holder and the disc 40 plifying the construction of the thermostatic head, on which rests an over-center sprin'g'fieledevices in which employed. ment or snap disc I0, comprising a convexo- A- further object is to provide either fixed or concave disc of spring materialfth'e; center of adjustable means whereby any degree of sensiwhich may be actuated from one, to thejjother tiveness in the action of the bellows may be ob of two opposed A limited positions f witI' iIa nap tained,.said means also acting to limit the ext I the valve or switch. its periphery and around a central opening 9, 35-

pansionl or contraction of the bellows, and the The discv i a a pressure difierential between the two snap posisnapped into a, reverse form it :will hav tp tions. ertyof regaining its .original form-, wheny; the

With the abov and oth r je in w, the pressure snapping it into a reverse :or. concavoinvention may be said to comprise the construcconvex form is reduced, or, it may be so formed tion illustrated in the accompanying drawing, that it will remain in a reverse or concave-conhereinafter described, and set forth in the apvex form until forced back by a pressure applied pended claims, together with such variations and in the opposite direction. 55

In the drawing the snap disc is placed in the head of the bellows with the convex side up- .ward, and its center is connected to the bottom head 2 by a rod II, which prevents the bellows expanding until the internal pressure is such that it will cause the snap disc I0 tosnap into a reverse form, at which time the bellows will expand with a snap action, the disc and the lower head attaining a position as indicated by the dotted lines. The snap disc I0 is provided with holes l2 to permit free passage of the expansible fluid from one side of the disc to the other.

The u per edge l3 of the peripheral flange of the plate holder 1 acts as a shoulder l3 for the edge of the disc head 3 to rest upon in assembling the parts, thus preventing the edge of the disc head being forced down against the edge of the snap disc and binding it to such an extent that its action would be sluggish or retarded. Holes [9 are provided in plate holder 1 so as to permit free movement of the fluid therethrough and prevent any valve action which might retard the operation.

The upper edge M of the flanged central opening 9 in the plate holder acts as a stop which limits the downward movement of the center of the snap disc. This stop may be adjustable as indicated in Fig. 4 by a threaded sleeve l5 which is screwed into a flange 20 extending downward from the plate. In addition to acting as a stop, it also acts as a means for regulating the temperature or pressure differential between one snap position and the other. If the disc is allowed to snap past dead center, its tendency to return to its normal form when the pressure is reduced is much less pronounced than would be the case if the movement was stopped before reaching dead center. As an illustration, assume that it requires a ten pound pressure within the bellows to snap the disc and that the movement of the center of the disc is limited by the stop to a point where the disc will snap back to its original form when the pressure is reduced to say nine pounds. The pressure diiferential is one pound. Now if we allow the center of the disc to move still further toward dead center by unscrewing the stop, the pressure would have to be reduced still more before the disc would snap back to its original position. From the above it will be seen that the movement of the center of the disc must be limited to that which will produce the desired differential between the two snap positions, especially since it is very difiicult to'obtain uniformity of action in snap discs, due to various causes in manufacturing methods and processes.

In Fig. 1 the pressure is applied inside the bellows and it expands with increase in pressure. In Fig. 2 I show a modified form of construction employing the same snap principles except that the mechanism is assembled inside of a cup i6 and the pressure within the cup causes the bellows to contract or collapse. The lower end of the bellows is fastened to and soldered to the inner edge of a flanged or ring portion I! of the lower part of the cup. The upper end of the bellows is closed by a disc head 18 which is connected by a rod to the central portion of a double snap disc l0, supported by the plate holder 1 which rests on an annular shoulder 2| formed in the internal wall of the cup. It will be noted in this construction that two snap discs are used.

Any number of discs may be used to form a laminated disc which is highly desirable in thermostatic elements of this type where it is desired to obtain a very strong snap action. I prefer to use one or more discs sufficiently strong to resist expansion or contraction of the bellows at the minimum operating temperature or pressure.

The snap movement of the bellows may be used either direct to operate valves and switches, or, it may be. amplified by any suitable lever system connecting the moving end of the bellows with the valve or switch to be operated.

Fig. 4 illustrates clearly the assembly of the snap disc in its dished plate holder 1 together with the adjustable stop I 5. the thermostatic element, the disc is placed in the holder and the stop adjusted at a point which will produce the desired difierential between the two snap positions. The disc is kept with the plate holder until the two are assembled within the bellows. This insures uniformity in action in all the thermostatic elements adjusted for the same differential between the two snap positions, which is highly desirable in all thermostatic devices. The adjustment makes it possible to obtain any desired differential between the two snap positions.

It will be understood that many modifications and various arrangements may be made in the construction of the snap acting thermostatic ele- 1. A thermostatic device of the character described comprising a flexible metallic bellows arranged to expand or contract in length in response to pressure changes, a snap acting spring element within said bellows, means for supporting the edges of said spring element in the walls of one end of said; bellows, and means connecting the central portion, of said spring element to the other end of said bellows, whereby when the bellows expands or contracts the spring element will be snapped from one position to the other and cause the bellows to expand or contract with a snap action. I

2. A thermostatic device as described in claim 1 and adjustable means for limiting the movement of the central portion of the spring element.

3. A thermostatic device of the characterde-r scribed comprising a metallic bellows closed at both ends and arranged to expand or contract in length in response to pressure changes, an annular shoulder formed in the walls of one end of the bellows, a dished plate having a. flanged edge extending'upwardly and resting upon the annular shoulder between the annular shoulder and the top closure, a convexo-concave snap acting spring disk supported on said dished plate, and means connecting the central portion of the snap acting disk with the other end of the be] lows, whereby, when the bellows expands or con tracts in response to pressure changes, the snap acting spring disk will be snapped from one position to the other and cause the bellowsto expand or contract with a snap action.

whereby the movement of the central portion of the snap acting spring disk may be limited.

' SIDNEY P. VAUGHN.

In manufacturing 1 

